This invention relates to photographic film processing apparatus and, more particularly, it concerns an improved method and apparatus for developing and projecting photographic film contained in a multipurpose cassette.
Cinematographic systems employing a programmable viewing apparatus and multipurpose cassette containing a photographic film strip together with a supply of processing fluid so that the film strip may be exposed in a camera and subsequently processed and projected in the programmable viewing apparatus are the subject of several issued U.S. Patents and pending applications commonly assigned to the assignee of the present invention. For example, U.S. Pat. No. 3,851,958, issued to Edwin H. Land on Dec. 3, 1974 describes a multipurpose cassette, motion picture system while U.S. Pat. No. 3,895,862 issued on July 22, 1975 to Joseph A. Stella, et al. is directed to a cassette arrangement for the above-noted system. A recent development of the viewing apparatus for such systems is exemplified by a copending application, Ser. No. 756,426, filed by M. T. Chambers and H. L. Hardy on Jan. 3, 1977.
The strip of film, as supplied with the cassette, is initially wound on a supply spool and advanced to a take-up spool when the cassette is placed in an appropriate camera for exposure in essentially conventional fashion. After exposure, the cassette is placed into a viewing apparatus capable of activating a cassette contained processor to deposit a uniform layer or coating of processing fluid along the length of the film strip as it is rewound from the take-up spool back to the supply spool. Thereafter, the series of successive transparent image frames formed on the film strip may be viewed by projection and rewound for subsequent projection cycles as desired.
In the current state of the art, successive convolutions of the film strip wound on the cassette take-up or supply spool are separated by a pair of parallel raised "rails" extending along the longitudinal margins or edges of the film strip. When the processing fluid has been deposited on the emulsion surface of the film strip and the wet film has been wound on the cassette supply spool, the rails serve to space successive convolutions or layers sufficiently so that no mechanical contact is made with the wet emulsion. However, if the film is wound too tightly on the supply spool, successive convolutions of the film may be drawn into contact despite the rails and produce undesirable transfer patterns on the processed positive transparency. Consequently, it is important that the film strip be kept from winding too tightly on the supply spool during the period following deposition of processing fluid on the film.